Film thickness control apparatus

ABSTRACT

A coating system for a continuous strip comprising a roller means station and an air knife station spaced from and vertically above the roller means station with a fluid depositing means located between the roller means station and air knife station.

United States Patent 1 Sievert et a1.

[ Jan. 8, 1974 FILM THICKNESS CONTROL APPARATUS [75] Inventors: WilliamC. Sievert, Chesterton;

William A. Carter, Gary; James L. Munson, Highland, all of Ind.

[73] Assignee: Inland Steel Company, Chicago, 111. 22 Filed: May 13,1971 21 App1.No.: 142,927

[52] US. Cl 118/63, 118/325, 118/415 [51] Int. Cl. B05c ll/06, B05c 5/00[58] Field of Search 118/63, 415, 21,

[56] References Cited UNITED STATES PATENTS 1,604,941 Hofmann 1 18/63 X1/1946 Groncy 118/415 2,393,502 2,583,220 1/1952 Lanigan 117/64 RFOREIGN PATENTS OR APPLICATIONS 807,805 1/1959 Great Britain 118/63Primary ExaminerJohn P. McIntosh Attorney-Merriam, Marshall, Shapiro &Klose [5 7] ABSTRACT A coating system for a continuous strip comprisinga roller means station and an air knife stationspaced from andvertically above the roller means station with a fluid depositing meanslocated between the roller means station and air knife station. I

10 Claims, 1 Drawing Figure msmwm 8M4 3.783.823

IIIIIIIII'I'III INVENTORS.

' WILLIAM C. SIEVERT WILLIAM A.CARTER JAMES L. MUNSON 771W WW ATTORNEYS.

1 FILM THICKNESS CONTROL APPARATUS In the coating of strips of materialsuch as metal, it is often desired to coat one side of the materialwithout coating the other side. For example, in the process ofgalvanizing metal, a continuous metal strip is coated on one side with amaterial which will prohibit any galvanizing-occurring on that side ofthe material. Subsequently, the strip is subjected to a hot dipgalvanizing step which will coat one side of the strip with zinc butwill not coat the previously coated side of ths strip.

Often the coating fluid or materials will have low viscosities(essentially water) such that the problem of preventing the fluid fromwrapping around the side of a strip opposite to the side which is to becoated is quite significant.

Moreover, it is important to regulate the thickness of the coatingmaterial that is deposited on a metal strip so that a uniform fluidcoating is deposited on the strip.

In our pending U.S. Pat. application S.N. 91,914 filed Nov. 23, 1970 nowU.S. Pat. No. 3,716,019, we have disclosed a method and apparatus forproviding a coating system which permits uniform coating of a strip witha fluid, including those having low viscosities, with no fluid wraparound. While this system, which includes the roller coating of fluid,has a number of advantages over the prior art, it is limited in certainrespects to line speeds that are tolerable with a roller coating system.

What is desired is to increase the line speed of a strip which is to becoated, In some instances, depending upon the viscosity of the coatingmaterial, it is possible to operate at line speeds of approximately 500to 600 feet per minute. If this line speed is increased to 1,000 feetper minute and higher, a drawback exists in that, when coating with asystem which includes rollers which regulate provide a uniform coatingof fluid, an increase in line speed causes a corresponding increase inthe speed of the rollers to such an extent that coating fluid is thrownoff the coating rollers before it is deposited on the strip. The resultof this increased centrifugal force is that a non-uniform coating isdeposited on the metal strip.

Further, in some instances, it is necessary to deposit the coatingmaterial on the top side of the strip only without wrap around to thebottom side of the strip because as the strip passes beyond the coatingstation, it often will pass over rollers would remove or affect theuniformity of a fluid coating that had been deposited on the bottom sideof the strip. Accordingly, in these instances, it is important that themetal be coated on the top side of the strip.

In order to obviate deficiencies with conventional systems presentlyused and to increase the line speed of a continuous metal strip, it isdesired to employ an air knife coating system. However, in order to usean air knife system such as exemplified in U.S. Pat. Nos. 3,117,847 and2,583,220, it is necessary to have the coating material spread entirelyacross the width of the metal strip without any wrap around of thecoating material to the opposite side of the strip prior to the strippassing under the air knife. Additionally, the coating system must beable to prevent wrap around when a fluid, including those that have lowviscosities (essentially water), are used in coating the strip.

SUMMARY OF THE INVENTION It has been found that if a fluid depositingstation is suitably placed between an air knife means and a rollerwhereby a coating material can be deposited on a strip prior to thestrip passing to the air knife station such that there is a gravityflow-back of the material to the roller in a direction opposite themovement of the strip, the strip can be properly treated without anywrap around prior to reaching the air knife station. At the air knifestation, an air knife can be employed to regulate the coating to providea uniform fluid coating on the strip.

As a result, a strip can be coated on one side only with fluids,including those of low viscosities, at a line speed significantlyincreased over those presently available.

Accordingly, the invention disclosed and claimed herein relates to theuniform coating of a continuous strip of material without wrap around inwhich high line speeds can be utilized in association with a new, novel.and unobvious association of an air knife and a fluid coating stationlocated on the upstream side of the air knife station.

The system involves initially passing a continuous strip under a firstroller located upstream of an air knife station. The roller ispositioned vertically below the air knife station so that a strip willbe angled upwardly toward the air knife station after it passes theroller.'Be-

tween the first roller and air knife station there is located a fluiddispensing or depositing means which releases fluid onto the surface ofthe strip. The fluid as it contacts the strip, flows by gravity backtoward the first roller where a damming action occurs at the nip orinterface of the entry roller and strip. The fluid is spread out acrossthe entire width of the strip and the roller which applies sufficienttension to thestrip so that the fluid, as it reaches the side of thestrip, will be squeezed off the strip and fall into a collecting panpositioned below the strip without wrapping around the strip.

As the coated strip passes downstream to the air knife station, the airknife provides for a uniform fluid thickness with any excess fluid beingsqueezed or forced out and away from the strip so'that fluid wrap arounddoes not occur.

The system also includes a second downstream, backup roller which servesto assist in providing the necessary tension in the strip between thetwo rollers.

Other features and advantages are inherent in the structure claimed ordisclosed and will become apparent to those skilled in the art from theforegoing detailed description in conjunction with the accompanyingdiagrammatic drawing.

DESCRIPTION OF THE DRAWING The drawing discloses a fragmentary side viewof a portion of a continuous strip situated relative to the stripcoating system of the present invention.

DESCRIPTION OF THE EMBODIMENT Referring to the drawing, there is shownacontinuous strip 10 which is to be coated with a fluidon one side ofthe strip only. As strip 10 progresses towards air knife station 12, itinitially passes under entry roller 14 and under fluid depositingstation 16. I I

As strip 10 travels through the line, fluid depositing means 15 isactuated to deposit fluid on the strip. The

fluid is deposited on inclined strip in such a manner that the fluidwill flow back, by gravity, toward entry roll 14 where it will dam up atthe strip roller interface 19. The damming action causes the fluid tospread out over the entire width of the strip. At the edge of the strip,the fluid, because of the pressure at the interface of roll 14 and strip10, will not wrap around the strip but will be squeezed away or forcedoutward from the edges of the strip sufficiently to prevent the fluidfrom being drawn onto the bottom side of strip 10 where no coating isdesired. The excess fluid is permitted to drip into one or more fluidcollecting pans 8 located below each edge of the strip. The fluiddrippage occurs approximately one-half inch away from the respectiveedges of the strip.

Roller 14 must be level and not tilted transversely for a slight tilt ofroll 14 will cause a fluid coating to wrap around to the bottom surfaceof strip 10.

As the strip leaves the area of roller 14, it passes under fluiddispensing station 16 where additional fluid is deposited on the stripsuch that as strip 10 passes downstream of station 16, an uneven coatingof fluid is dispensed on the top side 21 of strip 10. However, as strip10 continues further downstream, it passes under air knife whichcomprises a slotted member 32 which extends transverse to, at least, theentire width of strip 10. The slot is preferably about 0.03 inches inwidth.

Air knife 30, which dispenses a suitable gas, such as air, is employedto regulate and provide for a uniform coating thickness across theentire width of strip 10. The air knife is preferably locatedimmediately above and in axial alignment with roller 18, however the airknife may be positioned at a location between the fluid depositing meansand the roll 18. This assures that at the location of film regulation byknife 30, the strip is flat across its entire width. The distancebetween the nozzle and the strip in addition to the strip speed, airknife slot opening,'pressure of the gas exiting from slot 21 all affectthe regulation of the thickness of the film to be deposited on thestrip. By adjusting one or more of these variables, the desired coatingthickness can be procured. Any excess coating is forced away from theedges of the strip so that no wrap around of the coating fluid occurs atthe air knife station. The excess fluid forced away from the edges ofstrip 10 will be deposited in pan 8. Because the initial coating of thestrip has already occurred at roller station 14, the final regulation ofthe fluid thickness so as to procure a uniform coating thickness isreadily accomplished at air knife station 16.

in carrying out the fluid coating operation of the present invention, itis necessary that the strip, at least between interfaces l9 and 31, beunder tension to make certain that strip 10 is wrapped on roller 14along the entire width of the strip. This will assure that coating fluidis deposited across the entire width and additionally will permit theuse of strips, which have a wavelike configuration, because at the pointwhere the strip contacts roller l4, the strip will be flat across itsentire width.

Rollers l4 and 18 are adjustable vertically and h0rizontally. Therollers need not be independently driven but rather can turn at the samespeed as the strip passing through the system. The rollers are adjustedrelative to each other so that a downward angle a exists between thestrip in a substantially horizontal position and the inclined positionof the strip between the interfaces 19 and 31. Angle a must besufflcient to permit gravity feed back of the fluid whereby fluiddeposited on strip 10 at station 16 feeds back to roller 14. While ithasbeeiifixundflfat fiafigi'fifapp'roxifnately 10 has been satisfactoryin one application, the angle will depend upon the viscosity of thefluid being deposited on strip 10. Further the flow rate of the fluidfrom dis pensing means 16 should also be controlled to avoid excessivedamming at the roll-strip interface.

The foregoing detailed description has been given for simplicity andcleamess of understanding only and no unnecessary limitations should beunderstood therefrom as modifications will be obvious to those skilledin the art.

What is claimed is:

1. Apparatus for depositing fluid on a strip, said apparatus comprising:

a first entry damming roll means adapted to be positioned above andcontiguous to a strip to be coated, for providing a dam at the interfaceof a strip to be coated and said roll;

a second exit roll means located downstream of and adapted to bepositioned below and contiguous to a strip to be coated;

the uppermost surface of said second roll means being higher than thelowermost surface of said first roll means whereby a strip to be coatedis inclined upwardly from said first roll means to said second rollmeans;

a fluid depositing means positioned downstream of said first roll meansand between said first roll means and second roll means;

an air knife means for providing a uniform fluid coating on a strip tobe coated, said air knife station being positioned at a location from apoint adjacent said fluid depositing means to a point above said secondroll means; and,

said fluid depositing means and air knife means being positioned on thesame side of a strip to be coated as said first roll means;

whereby fluid which is adapted to be deposited on said strip is dammedat the interface of said first damming roll means and a strip to becoated.

2. The apparatus of claim 1 wherein said first roll means is adjustableboth vertically and horizontally.

3. The apparatus of claim 1 wherein said second roll means is adjustableboth vertically and horizontally.

4. The apparatus of claim 1 wherein said air knife means is positionedabove and in axial alignment with said second roll means.

5. The apparatus of claim 1 wherein said first roll is substantiallylevel and free of tilting transversely.

6. Apparatus for depositing fluid on a strip, said apparatus comprising:

a first entry damming roll adapted to be positioned above and contiguousto a strip to be coated for providing a darn at the interface of a stripto be coated and said roll whereby a coating fluid can be depositedacross the entire width of a strip to be coated;

said first roll being adapted to exert sufflcient pressure at saidinterface whereby a fluid will be spread across the width of a strip andat the side of the strip will be squeezed away'from the edges of a stripto be coated;

a second exit roll located downstream of and adapted to be positionedbelow and contiguous to a strip to be coated;

the uppermost surface of said second roll means being higher than thelowermost surface of said first roll whereby a strip to be coated isinclined upwardly from said first roll to said second roll;

fluid depositing means positioned downstream of said first roll andbetween said first roll and said second roll;

an air knife means for providing a uniform fluid coating on a strip tobe coated, said air knife station being positioned at a location from apoint adjacent said fluid depositing means to a point above said secondroll; and,

said fluid depositing means and knife means being positioned on the sameside of a strip to be coated as said first roll whereby fluid which isadapted to be deposited on said strip is dammed at the interface of saidfirst damming roll and a strip to be substantially level and free oftilting transversely.

P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,783,323 Dated JanuaryB, 1974 Inventor) William C. Sievert et al. 7

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col. .1, line 38, insert -and-- between "regulate" and "provide".

Col 1, line 50, insert --which-- between "rollers" I "would" Col. 3,line 35, after "18" insert ,however the 'air knife may be positioned ata location between the :fluid depositing means and the roll l8-.

Signed and sealed this 18th day of June 1974;

(SEAL) Attest:

EDWARD M.FLETCHER,JR. v C. MARSHALL DANN Attestlng Officer Commissionerof Patents 7

1. Apparatus for depositing fluid on a strip, said apparatus comprising:a first entry damming roll means adApted to be positioned above andcontiguous to a strip to be coated, for providing a dam at the interfaceof a strip to be coated and said roll; a second exit roll means locateddownstream of and adapted to be positioned below and contiguous to astrip to be coated; the uppermost surface of said second roll meansbeing higher than the lowermost surface of said first roll means wherebya strip to be coated is inclined upwardly from said first roll means tosaid second roll means; a fluid depositing means positioned downstreamof said first roll means and between said first roll means and secondroll means; an air knife means for providing a uniform fluid coating ona strip to be coated, said air knife station being positioned at alocation from a point adjacent said fluid depositing means to a pointabove said second roll means; and, said fluid depositing means and airknife means being positioned on the same side of a strip to be coated assaid first roll means; whereby fluid which is adapted to be deposited onsaid strip is dammed at the interface of said first damming roll meansand a strip to be coated.
 2. The apparatus of claim 1 wherein said firstroll means is adjustable both vertically and horizontally.
 3. Theapparatus of claim 1 wherein said second roll means is adjustable bothvertically and horizontally.
 4. The apparatus of claim 1 wherein saidair knife means is positioned above and in axial alignment with saidsecond roll means.
 5. The apparatus of claim 1 wherein said first rollis substantially level and free of tilting transversely.
 6. Apparatusfor depositing fluid on a strip, said apparatus comprising: a firstentry damming roll adapted to be positioned above and contiguous to astrip to be coated for providing a dam at the interface of a strip to becoated and said roll whereby a coating fluid can be deposited across theentire width of a strip to be coated; said first roll being adapted toexert sufficient pressure at said interface whereby a fluid will bespread across the width of a strip and at the side of the strip will besqueezed away from the edges of a strip to be coated; a second exit rolllocated downstream of and adapted to be positioned below and contiguousto a strip to be coated; the uppermost surface of said second roll meansbeing higher than the lowermost surface of said first roll whereby astrip to be coated is inclined upwardly from said first roll to saidsecond roll; fluid depositing means positioned downstream of said firstroll and between said first roll and said second roll; an air knifemeans for providing a uniform fluid coating on a strip to be coated,said air knife station being positioned at a location from a pointadjacent said fluid depositing means to a point above said second roll;and, said fluid depositing means and knife means being positioned on thesame side of a strip to be coated as said first roll whereby fluid whichis adapted to be deposited on said strip is dammed at the interface ofsaid first damming roll and a strip to be coated.
 7. The apparatus ofclaim 6 wherein said first roll is adjustable both vertically andhorizontally.
 8. The apparatus of claim 6 wherein said second roll isadjustable both vertically and horizontally.
 9. The apparatus of claim 6wherein said air knife is positioned above and in axial alignment withsaid second roll means.
 10. The apparatus of claim 6 wherein said firstroll is substantially level and free of tilting transversely.